The time division duplex (TDD) mode, as one of the two basic duplex systems, has got more and more attention under a constant growth of the demand for the bandwidth of broadband mobile communication. Uplink and downlink transmissions in the TDD system use the same frequency resource, and uplink and downlink signals are transmitted in different time slots. In a common TDD system such as 3rd Generation (3G) Time Division Synchronized Code Division Multiple Access (TD-SCDMA) system and 4th Generation (4G) TD-SCDMA Long Term Evolution (TD-LTE) system, division of uplink and downlink time slots is static or semi-static. Generally, the division ratio of uplink and downlink time slots may be determined based on a cell type and a rough service scale in a network planning and may remain unchanged. That is easy and effective in the context of large coverage of macro-cell. FIG. 1 shows a frame structure of the TDD mode specified in the 3rd Generation Partnership Project (3GPP) LTE (Version) Rel-8/9/10. The supported uplink and downlink sub-frame configurations include the seven ways shown in Table 1.
One radio frame has a length of 10 ms, including 10 sub-frames classified as special sub-frames and normal sub-frames, the length of each sub-frame is 1 ms. The special sub-frame includes three sub-frames: a Downlink Pilot Time Slot (DwPTS), a Guard Period (GP) between an uplink frame and a downlink frame, an Uplink Pilot Time Slot (UpPTS). The normal sub-frame includes an uplink sub-frame and a downlink sub-frame configured to transmit uplink/downlink control channels and service, etc. One radio frame may be configured with two special sub-frames (in sub-frames 1 and 6) or with one special sub-frame (in sub-frame 1). The sub-frames 0 and 5 and the DwPTS sub-frame of the special sub-frame are always reserved for downlink transmission, the sub-frame 2 and the UpPTS sub-frame of the special sub-frame are always reserved for uplink transmission, and other sub-frames may be configured for uplink transmission or downlink transmission as needed.
TABLE 1config-urationlength ofsub-frame numbernumberone sub-frame012345678905 msDSUUUDSUUU15 msDSUUDDSUUD25 msDSUDDDSUDD310 ms DSUUUDDDDD410 ms DSUUDDDDDD510 ms DSUDDDDDDD65 msDSUUUDSUUD
With the development of the network, 3GPP TR36.828 and some of 3GPP conferences publish several designing schemes of signaling, to support a flexible uplink-downlink (UL-DL) sub-frame configuration in a TDD cell. One of the schemes is that a base station sends information indicating a TDD uplink-downlink sub-frame configuration to a user equipment via a physical layer control channel or signal, to notify the user equipment current uplink-downlink sub-frame configuration information of a cell. The physical layer control channel herein may adopt a physical channel such as specific DCI (Downlink Control Information) format of a physical downlink control channel (PDCCH) or a physical broadcast channel (PBCH).
The present physical layer control channel such as PDCCH and PBCH does not have a hybrid automatic repeat request (HARQ) mechanism. The user equipment may not learn an uplink-downlink sub-frame configuration in a current radio frame if the user equipment does not demodulate correctly a physical layer control signaling carrying uplink-downlink sub-frame configuration information, thereby a sub-frame for blind-detecting the PDCCH or an enhance PDCCH and an uplink-downlink HARQ timing may not be determined. At this point, the user equipment cannot communicate with the network normally during the uplink-downlink sub-frame reconfiguration period, thereby causing a significant drop of user throughput.
To sum up, at present, the user equipment cannot communicate with the network normally if the user equipment does not receive correctly the physical layer control signaling carrying uplink-downlink sub-frame configuration information sent from the network side, thereby causing a significant drop of user throughput.